Method of making asbestos-cement sheets



Feb. 16, 1954 c. c. SMITH 2,669,166

METHOD OF MAKING ASBESTOS-CEMENT SHEETS Filed Aug. 16, 1949 2 SheeisSheet 1 IN VEN TOR.

Feb. 16, 1954 C. C. SMITH METHOD OF MAKING ASBESTOS-CEMENT SHEETS 2 Sheets-Sheet 2 Filed Aug. 16, 1949 INVENTOR.

BY I

Patented Feb. 16, 1954 UNITED-STATES PATENT OFFICE METHOD OFMAKING ASBESTOS-CEMENT SHEETS 4 Charles Carter Smith, Mobile, Ala., assignor to The Ruberoid 00., New'York, N. Y., a corporation of New Jersey Application August 16, 1949, Serial No. 110,564

method. According to that method a pulp or slurry of Portland or hydraulic cement and asbestos fibers is formed in one or more cylinder vats or tanks and is picked up on an endless belt or band, usually made of felt, by which it is carried to an accumulator drum or roll where it is wound, a'nurnber of times, until the desired thickness of laminated material has been obtained.

The material is then slit, stripped from the drum, and laid out fiat. The apparatus used in carrying out that method is known in the art as a Hatschek machine, and is quite expensive.

1 The Hatschek process is subject to several objection's and disadvantages, among others, that it is intermittent in that when the laminated materialhas been formed to the desired sheet thickness it must be stripped from the accumulator drum;' and, that the sheets so formed are limited in length to the circumference of the accement sheets that permits of; use of thepresent Hatschek machines.

Another object of the invention is to provide a method of making laminated asbestos-cement sheets of indeterminate lengths.

A further object of the invention is to increase the rate of production of the sheets.

A still further object is to decrease the cost of manufacture by reducing the amount of labor and handling required.

According to the present invention a laminated sheet isformed by sandwiching a layer of a dry mixture of cement and fibers between two continuous webs of asbestos-cement to produce a composite laminated sheet consisting of two outer layers and an intermediate layer or filler, the three layers preferably being of substantially the same average thickness. The sheet so made may be cut to form sidings, roofing shingles, or other products, which products may be textured and, if desired, faced with granules, in the usual manner. The sheet is usually made so that when pressed its thickness would be approximately 0.150", each layer being about 0.050" thick. It is to be understood, however, that these dimensions are merely illustrative. The product made by the practice of my invention is cheaper for method of making I 1 Claim. (Cl. 92-40) the same finished thickness than that made by the conventional methods.

The invention will appear more fully from the following description thereof, reference being had to the accompanying drawings, in which:

.Fig. 1 is a perspective view of one form of apparatus, suitable for use in conjunction with a Hatschek machine, in carying out my invention;

Fig. 2 is a top plan view of that apparatus;

Fig. 3 is a diagrammatic view in elevation of one form of complete apparatus, including a conventional Hatschek machine;

Fig. 4 is a schematic top plan view of one form ,of hopper for use in applying the intermediate layer or filler of dry mix; and,

slurry is deposited on the lower contacting surface of the endless belt l2. The thickness of the web 13 formed on the belt is, in general, determined by the number of vats used. The web is carried by the belt over the conventional suction box l4 and under the accumulator drum or roll I5.

In the practice of my invention the drum [5 of the Hatschek machineis not used to wind the web, in the manner in which it usually functions, but is usedsolel'y to feed the web on to the conveyor 16. If desired, the accumulator drum may be replaced by a feed roll.

The conveyor 16 carries the web under and in contact with a rotary slitter I! that severs the web into two parts or sheets I3a and l3b of equal width. The sheet l3a. is carried downwardly on to the horizontal conveyor l 8, while the sheet I3!) is carried sidewise on the conveyors l9 and into superposition with the sheet 13a. In the progress of the sheet 13a it passes under a hopper 20 by which a layer 2| of dry mix of the desired thickness is deposited upon the upper surface of the sheet l3a. The dry mix consists preferably of a mixture of Portland cement and ground asbestoscement waste in suitable proportions. Substantially equal parts of cement and waste have been found to give satisfactory results. The mix may be applied by any conventional vibrating screen 22. Where it is desired to make a tapered product the screen may be wider along one edge of the sheet than along the other, as seen in Fig. 4, so that as the sheet travels under the hopper the thickness of the mix deposited on the surface will gradually reduce in thickness from one edge to- 3 wards the other. The moisture contained in the sheet may be sufiicient to hydrate the dry cement mix, but if not the dry mix after application may be sprayed with water.

While for the sake of economy I prefer to use a single web l3 of asbestos-cement and split it into twbifihets Rwanda 3b, it iis wlthin the scope of my "invention to start with two separately formed sheets if desired. The latter procedure, however, is much more expensive as it requires use of two Hatschek machines instead ofone. Moreover, for best results itis important tha'tthe two outer asbestos-cement layers be of exactly the same thickness. That result idllows riatufal-ly from splitting a single weblong'ltudin'ally into two sheets but is difficult to attain to the required degree when the two sheets are Separately-01311;

In the particular apparatus illustratedin the drawings the sheet l3b passes upwards an'ddownwards in its path of travel toward the sheet 13a.

Whisvismerely an expedient to provide "space hetween the sheets for the l'iopper -ZIJ. 'The form'of th'e 'apparatus is immaterial, 'the essentia1 feature ie 1 that the two sheets, "after having "been severed longitudinally from a single :web or separately "termed, are "continuously progressed so that one *ofithe sheets 'is-su'perposed, smoothly and flatly, -upon the otlreraffter thedayer of'dry mix hasbee'n .applie'd'tothe latter.

The composite sheet may then be passed under 'a"hopper 2%bywhich}if desired-a 'facing'of-grou't, or of neat cement and granules, maybeapplied "for" thepurpos'e of-decorating or ornamenting' the matefiall,"after which it passes between 'plessrolls 24, and is finally cult by thei-rotaryhutter 25, or "v Oth1ciitting instrumentality, "into pieces or the size and shape of the finishedjproduct. The'cut "set in in'g moti'on it travels "from "slitt'er IT to the ipoint-"where' it comes 'into superposition"withwhe "sheet litaso astoiassurethat the"two-sheets'*will meet in exact-parallelism. The r611 that carries 't'hefrotary fsli'tter H may in'addition' cariycutters i 4 at its ends, as indicated in Figs. 1 and 2 or the drawings, to trim the edges of the web l3. The wet scrap cut from the edges may be returned to the vats HI, or it may be dried, set and ground for use in making the dry mix. The upper roll of the pair of press rolls 24 may be plain or it may have-a textured suriareefinimitation of wood t'exture or .other designfito'giVe the'upp' r surface of the pressedv composite sheet a texturedapvqiearance.

-What I-claimds; A method of making a laminated product which consists in continuously forming and longitudi- Y wally ieedinga imo'ist web of unset asbestos- "I5 cement, ficontinuously slittin the web longitudinailly asit is Tedto form two homogeneous sheets tofisuhstantiailymniform width, continuously and simultaneously feeding the two sheets longitudinally'o'ne above the other at the same rate of 0 speed, directing the upper of the two sheets laterailly at an angle into parallelism=-with the1dther, depositing ea idry mix-of hy'draul-i'c cement and asbestos flber uponthe upper surface or them-- der sheet while the cement o'f thesheetdsstill moist and unset before it i is brought' into contact *wit-hth'e upper sheewsuperposing the= uppereshe'et on said faced surface of the lower sheet, "pressing th'e'composite product.

Nmnber Date 

